[Bloat] Burst Loss

[Fred Baker]

On May 9, 2011, at 11:06 AM, Rick Jones wrote:

> GSO/TSO can be thought of as a symptom of standards bodies (eg the IEEE)
> refusing to standardize an increase in frame sizes.  Put another way,
> they are a "poor man's jumbo frames."

I'll agree, but only half; once the packets are transferred on the local wire, any jumbo-ness is lost. GSO/TSO mostly squeezes interframe gaps out of the wire and perhaps limits the amount of work the driver has to do. The real value of an end to end (IP) jumbo frame is that the receiving system experiences less interrupt load - a 9K frame replaces half a dozen 1500 byte frames, and as a result the receiver experiences 1/5 or 1/6 of the interrupts. Given that it has to save state, activate the kernel thread, and at least enqueue and perhaps acknowledge the received message, reducing interrupt load on the receiver makes it far more effective. This has the greatest effect on multi-gigabit file transfers.